Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.47	3.282%	$164.7038	$164.70	$164.70	$164.70
Purchase #2	$84.75	13.334%	$96.0506	$96.05	$96.05	$96.10
Purchase #3	$157.34	10.790%	$174.317	$174.32	$174.30	$174.30
Purchase #4	$70.85	11.303%	$78.8582	$78.86	$78.85	$78.90
Purchase #5	$47.97	13.707%	$54.5452	$54.55	$54.55	$54.50
Purchase #6	$221.74	7.366%	$238.0734	$238.07	$238.05	$238.10
Purchase #7	$229.66	10.538%	$253.8616	$253.86	$253.85	$253.90
7 purchase totals =	$971.78		$1,060.4098	$1,060.41	$1,060.35	$1,060.50